This application relates generally to gas turbine engines and, more particularly, to gas turbine engine aerodynamic devices.
A gas turbine engine typically includes a rotor assembly and a plurality of secondary cooling air circuits. To supply air to the secondary air circuits, engines include aerodynamic devices to deliver rotating airflow from one radius to another in order to avoid exceeding swirl limits of the air. One type of aerodynamic device uses a series of chambers which induce controlled rotation of the airflow as the air flows between chambers of various diameters. The chambers are formed either with individual tubes or parallel plates that include partitioning walls. Other known aerodynamic devices include curved passages instead of partitions to turn the flow in an opposite direction and capture a dynamic head of the airflow as well as shorten a height of the aerodynamic device.
For devices which use tubes as chambers, a length of the individual tubes used to form the chamber determines the aerodynamic effect obtained by the chamber. As the length of the tubes is increased, the aerodynamic effect obtained within the chamber is enhanced. However, the increased length of the tubes also increases the weight of the aerodynamic device and may adversely impact structural dynamics of the aerodynamic device. To overcome weight concerns, thin-walled tubes are used to form the chamber. Because thin-walled tubes are more susceptible to vibration, dampers may be installed within the tubes. The dampers increase the weight of the tubes and may increase the tube mean stress.
For devices which use parallel plates as baffles for chambers, during operation, connections between the parallel plates and the passages create multiple stress concentrations that amplify hoop stress present in the plates due to rotation. To reduce the effects of hoop stress concentration, contoured fillets may be installed around the transitional connection areas formed between the plate and partition. The fillets increase the weight of the tubes and increase the assembly costs of the rotor assembly.
In an exemplary embodiment, a gas turbine engine rotor assembly includes a plurality of aerodynamic devices to direct airflow radially inward in a rotating environment for use as cooling air within secondary cooling air circuits. The gas turbine engine rotor assembly includes a rotor shaft that includes a plurality of openings extending between an outer surface of the shaft and an inner surface of the shaft. The rotor shaft also includes a pair of flanges extending radially inward from the shaft inner surface and defining a pocket. Each aerodynamic device includes an opening and a contoured outer surface that permits the aerodynamic device to be positioned flush against an inner surface of the rotor shaft. The aerodynamic devices are sized to fit within the rotor shaft flange pocket and each device also includes a pair of vane segments. The vane segments define a curved passageway that extends from the aerodynamic device opening.
During operation, centrifugal forces generated within the rotor assembly force each aerodynamic device radially outward into each rotor shaft pocket. The rotor shaft flange retains the aerodynamic device such that the aerodynamic device opening and the rotor shaft openings are concentrically aligned. Air flowing through the gas turbine engine at a relatively high tangential velocity is directed radially inward through the aerodynamic devices for use as cooling air within downstream secondary cooling air circuits. The curved shape of the passageway defined by the vane segments causes the airflow to exit the aerodynamic devices after a high turning in an opposite direction, thereby permitting the aerodynamic device to be fabricated with a smaller size than known aerodynamic devices. A reduction in pressure losses due to the airflow re-direction is facilitated and the secondary cooling air circuits receive airflow at a sufficient pressure and temperature. Furthermore, because the aerodynamic devices are not formed circumferentially as a unitary structure, hoop stresses generated within the aerodynamic devices due to centrifugal body loads are reduced in comparison to known aerodynamic devices.